Most Common Blood Type
Blood group O is the most common blood type globally, followed by blood group A, with significant regional variation in distribution patterns.
Global Blood Type Distribution
The frequency of ABO blood groups shows consistent patterns across multiple populations, though regional differences exist:
Primary Distribution Pattern
- Blood group O: Most prevalent globally, representing approximately 34-52% of populations 1, 2
- Blood group A: Second most common, occurring in 19-40% of individuals 3, 4
- Blood group B: Third in frequency at 17-33% 3, 1
- Blood group AB: Least common, found in only 5-8% of populations 3, 4
Regional Variations
Western populations (including Russia and parts of Europe) demonstrate a pattern where blood group A may predominate over O, with frequencies reaching 37-40% 4. In contrast, South Asian and African populations consistently show blood group O as most prevalent, with frequencies exceeding 38-52% 1, 2.
The distribution pattern in South India follows: O > B > A > AB, while cardiovascular surgery patients in Russia showed: A > O > B > AB 4, 1. These variations reflect genetic evolution and population ancestry 2.
Rh Factor Distribution
Approximately 85-95% of individuals are Rh-positive (D antigen present), making Rh-negative blood relatively uncommon at only 5-8% of the population 5, 3, 2. This has significant implications for transfusion medicine and pregnancy management.
Clinical Significance
Universal Donor Status
Blood group O-negative represents the universal donor type that can be transfused to any patient, making it critically important for emergency situations 6. However, this blood type comprises only approximately 3-5% of most populations (combining O frequency with Rh-negative prevalence) 3, 2.
Disease Risk Associations
Blood type O individuals face higher risk for severe outcomes from certain infections, including cholera, where approximately 45% of the U.S. population with blood type O demonstrates increased susceptibility to severe disease 5.
Transfusion Planning
Understanding blood type distribution is essential for blood bank management. The pattern O > A > B > AB guides inventory planning, with particular attention to maintaining adequate O-negative supplies for emergency use 4, 2.
Rare Blood Types
Rare phenotypes include:
- K+k- (Kell system): 0.06% frequency 3
- Bombay phenotype (Oh): Extremely rare at 0.004% 1
- Rh null and other complex phenotypes: Less than 0.003% 3
These rare types require specialized donor registries for patients with corresponding antibodies or phenotypes 3.